Silver salt diffusions copyimg method

ABSTRACT

Silver salt diffusion transfer method, wherein an image is formed by exposure on the silver halide emulsion layer of a negative sheet and the thus exposed negative sheet is developed by a developer liquid, whereupon the developed image is transferred by pressure contact to a receiving sheet. The invention provides that the receiving sheet is uncoated sheet material which, prior to the pressure contact with the negative material, is moistened with a liquid of different composition than said developer liquid, the liquid comprising an aqueous alkaline or acidic solution containing a substance exhibiting amphoteric properties and being capable of reducing silver salts to silver.

United States Patent Wendt 7 51 Jan. 25, 1972 [21] Appl. No.: 703,026

[73] Assignee:

3,450,535 6/1969 Limberger et al. ..96/29 2,686,717 8/1954 Land ..96/29 3,510,301 4/1970 Limberger ..96/29 3,510,302 4/1970 Limberger et al. ..96/29 Primary Examinerw-Norman G. Torchin Assistant Examiner-John L. Goodrow Attorney-McGlew and Toren 57 ABSTRACT Silver salt diffusion transfer method, wherein an image is formed by exposure on the silver halide emulsion layer of a negative sheet and the thus exposed negative sheet is developed by a developer liquid, whereupon the developed image is transferred by pressure contact to a receiving sheet. The invention provides that the receiving sheetis uncoated sheet material which, prior to the pressure contact with the negative material, is moistened with a liquid of different composition than said developer liquid, the liquid comprising an aqueous alkaline or acidic solution containing a substance exhibiting amphoteric properties and being capable of reducing silver salts to silver.

, 5 Claims, 1 Drawing Figure SILVER SALT DIFFUSIONS COPYIMG METHOD A method of the general nature referred to is disclosed in, for example German Pat. No. 764,572. Generally, the negative material and the receiving material are wetted in a common bath. The cited German patent indicates a suitable concentration of the reaction compounds used in the developer, so that the primary picture layer can be in contact with the receiving layer already prior to the development of the picture (two-layer material) such that the development of the primary picture and the transfer of the secondary picture can be effected in one and the same process. In order to improve the transfer and diffusion properties, there may be present substances dissolving silver halides, such as, for example, sodium thiosulphate and/or reacting substances which produce in the medium difficulty soluble silver compounds and/or compounds which form developing nuclei or are such nuclei, such as, for example, sodium sulphite, stannochloride, and others.

The practical embodiment of this method for commercial use with foliate copying material comprises separate positive or receiving layers containing reducing nuclei. This layer is arranged on a special carrier such that layer and carrier form together the receiving material.

The term material as used in the following specification comprises also foliate materials.

The said patent specification mentions also a multilayer material as negative material. With this material, the receiving layer is applied to a carrier and an unhardened silver halide solution is poured over the receiving layer. According to the German Pat. No. 1,171,740, the receiving layer is applied as covering layer over the negative layer. According to this latter patent, this layer need not contain reducing nuclei, and these are supplied by the treatment liquid to the colloidal receiving or covering layer.

Such reducing nuclei are: sulphides, selenides, polysulphides, polyselenides, thiourea, mercaptanes, stannous halides, heavy metals and their salts and cloudy silver halide, suplphides of heavy metals such as antimony, bismuth, cadmium, cobalt, lead, nickel and silver. In this connection, heavy metals, for example, silver, gold, platinum, palladium and mercury, particularly in colloidal form, as well as the noble metals are most efficient.

This method of producing pictures on a normal unlayered receiving material has not been adopted in practice, because substantial drawbacks were encountered with regard to the durability of such alkaline developing solutions containing developing nuclei.

The Belgian Pat. Nos. 635,811 through 635,813 describe a modification of the known method with two distinct sheets for the receiving and negative materials, which has become known as the Copyrapid-Dry Method. However, according to Belgian Pat. No. 635,81 1, the production of pictures or copies on an unprepared receiving material has not been successful. In principle, an additional special layer was provided on the negative material and developing nuclei were to be supplied thereto by the treatment fluid. ln addition, the coating of the receiving material has again been adopted in order to produce copies which are as dry as possible. The coating of the receiving material contains fillers. This method is based on the consideration that at least a thin layer of the additional coating of the negative material is transferred to the receiving material. In this respect, this method is characterized by a physical transfer of coating. The originally bad adhesion of the originally proposed treatment liquid was avoided by incorporating the developing nuclei and/or the substances capable of forming these nuclei again into the receiving layer and ad ding the developing substances both to the negative and to the positive materials. The treatment liquid is here merely a socalled activator.

For producing a picture or copy on an unlayered or uncoated receiving material, it has been proposed to develop, after exposure, a negative material which is coated with a water-permeable layer and contains developing substances. The development is then carried out by means of an alkaline solution free from developing nuclei and developing substances. This solution is brought into contact with an uncoated receiving sheet which has been impregnated in an aqueous solution containing developing nuclei and more particularly noble metal nuclei. This method, which is also based on the silver salt diffusion copying method yields copies, the quality of which is comparable with those obtained by the known silver salt diffusion method on an uncoated sheet. The used liquids are not subject to any disadvantages either from the viewpoint of durability, or from that of their use for the development of the negative or for the impregnating of the positive material. The execution of this method and especially the production of the associated apparatus, however, is costly and requires expensive safeguards due to the fact that the transport of even minute quantities of one treatment solution into the other must be avoided, because otherwise the durability of the treatment solutions would be seriously impaired.

However, this method has the advantage that a usable silver picture is produced on an uncoated receiving material by means of the silver salt diffusion transfer method.

The present invention has the object of improving this method and of eliminating the incompatibility of two treatment solutions.

According to the invention, the treatment liquid for the receiving material is an aqueous alkaline or acid solution containing as reaction substance a substance with amphoteric properties and capable of forming, both in the alkaline and in the acidic ranges, compounds which are reducing agents and which can reduce silver salts.

In view of the amphoteric properties, these compounds can be formed both in the alkaline and in the acidic ranges. Tin (ll) salts and aluminum chloride are preferred amphoteric substances.

It has now been found surprisingly that, even with the use of different treatment solutions or liquids, the excellent durability is not impaired if a certain amount of one liquid is transferred into the bath of the other liquid during the execution of the method.

The term uncoated receiving material designates merely a foliate material which does not contain any film-fonning colloids. The material is wetted with an aqueous alkaline or acid solution only during the execution of the method for producing a copy.

Thus, the invention affords the possibility, not only of using simple and cheap materials, but also particularly sheets, e.g., of paper, which may have been imprinted preliminarily with other matter. In addition, the method makes use of a treatment liquid which is cheaper than the noble metal salt solutions hitherto proposed.

The term negative material" relates to a foliate element with a silver halide emulsion layer on which a water-permeable covering layer has been arranged as top layer. Preferably, this material contains developing substances or combinations of such substances, as well as tint improving substances and other materials favoring the execution of the silver salt diffusion method, and known in the art. Such a material is known and is commercially available as Copyrapid-Dry Negative."

The term activator solution means in its simplest form:

1 ,000 milliliters of water 75 grams of sodium phosphate 40 grams of sodium sulphite, sic

10 grams of sodium thiosulphate, sic

Further substances may be added to this solution for improving the picture tint, for regulating the developing speed, as well as substances favoring the silver salt diffusion, such as, e.g., l-phenyl-5mercaptotetrazol, potassium bromide, and the like.

Also this solution is known per se and is commercially available under the designation Copyrapid-Dry Activator."

The invention will now be described, by way of example, with reference to the following examples.

EXAMPLE 1 A negative material (CopyrapidDry negative) is exposed and brought into contact with a receiving material of paper, after development in the activator solution provided for this purpose; the receiving material has been wetted in a separate bath, having the following composition:

1,000 ml. activator solution 100 ml. 1 percent aqueous tin (ll) chloride solution 10 ml. 1 percent aqueous sodium hydroxide solution.

EXAMPLE 2 EXAMPLE 3 As in example I, but with a treatment liquid for the receiving material having the following composition:

1,000 ml. water 5 g. aluminum chloride A101,

0.5 g. caustic soda (NaOl-l) 0.5g. potassium bromide (KBr) This example contains AlCl as amphoteric substance.

EXAMPLE 4 As in example 1, but with a treatment liquid for the receiving material of an acid solution of tin (ll) chloride with the following composition;

1,000 ml. water 2.5 g. SnCl -2H H 2.0 g. NaOH 5 ml. HCl'conc.

EXAMPLE 5 As in example 4, but with a treatment liquid for the receiving material having the following composition:

1,000 ml. water 2.5 g. tin (ll) chloride 1.0 g. ascorbic acid 0.2 g. hydroquinone 0.5 g. potassium bromide.

EXAMPLE 6 Production of copies as described in examples I through 5. After producing the first copy, the light-sensitive material is again wetted with activator solution and pressed on to a receiving sheet wetted with the treatment solution specified for the positive. Thus, two positive copies are obtained from an exposed, light-sensitive material.

EXAMPLE 7 Production of copy as in examples I through 5.

After the manufacture of the first copy, the reverse of the receiving sheet may be subjected to the same steps in conjunction with another exposed negative. Thus, a two-sided positive copy is produced on the receiving sheet.

EXAMPLE 8 As in example i, but with a treatment solution for the positive sheet having the following composition:

1,000 ml. water 20 ml. 1 percent solution of hexachloroplatinum (IV) acid in water l.0 g. sodium chloride sic l0 ml. 1 percent solution of tin (lll) tetrachloride acid in water 0.5 g. sodium hydroxide 0.5 g. tin (ll) chloride.

Conveniently care is taken in constructing the apparatus that chambers are provided underneath the guide webs for the materials, adapted to receive the precipitate forming during the copying. Such guide webs may be, for example, webs elevated above the bottom of the bath, over which the foliate materials pass so that they are not in contact with the precipitate.

When the examples 1 through 5 were used, it was found that the treatment solutions for the receiving sheet could be reactivated after consumption of the reacting substances by adding new reaction concentrate, either in the form of salts or their solutions, or in the form of metal tin as foil or powder. It is also safe to add from the beginning sufficient quantities of the amphoteric substance and more particularly of metallic tin, whereby the utilization of the solution is substantially improved without impairing its functional capabilities. in addition, further substances may be added to the solution which favorably affect the silver salt diffusionmethod, such as, e.g., picture tint improving agents, substances preventing yellowing, and the like.

Moreover, it has also been found that, especially with the treatment solutions specified in examples highly and 2, the compatibility of the reacting substances has been improved to such an extent that the solution for developing the negative and the treatment solution for the receiving material can be combined in one bath without substantially impairing the durability or stability of the solutions or the quality of the copies produced thereby. With such treatment solutions, processing can be effected with apparatus, already commercially available, and constructed for carrying out the conventional silver salt diffusion method. In this way, a high-quality copy can be produced on uncoated receiving material in a very simple and high economical manner.

For explaining the invention operating only with a single bath, the following examples are given:

EXAMPLE 9 A negative material (Copyrapid-Dry Negative) is exposed and, after developing in an apparatus constructed for carrying out the conventional silver salt diffusion method, is brought into contact with an uncoated receiving sheet wetted in the same treatment solution. The single bath solution for carrying out this method has the following composition:

L000 ml. activator ml. 1 percent tin (ll) chloride solution 10 ml. 1 percent sodium hydroxide solution 25 ml. glycerin.

After a contact period which is sufficient for the silver salt diffusion transfer, the two materials are separated and a positive copy is obtained on the uncoated material sheet; this copy has excellent picture quality.

EXAMPLE 10 As in example 9, but with a treatment liquid having the following composition:

1,000 ml. activator 100 ml. 1 percent tin (ll) chloride solution 10 ml. l percent sodium hydroxide solution 5 g. ascorbic acid 1 g. hydroquinone 10 ml. glycerin l g. powdered tin. The method is described in conjunction with the accompanying drawing. 1 shows the receiving material. The negative material 5 is composed of the foliate element 2, the silver halide emulsion layer 3 and the covering layer 4. The figure shows that a document is exposed to the negative material 5 by means of an exposing lamp 7. For realization of the method a device can be used which has a first bath 8 with an activator solution and a second bath 10 with a treatment liquid ll. in bath 10 rotates a wetting-roller 12. Above this wetting-roller a guide element I3 is arranged, which guides the receiving material over the wetting-roller. Behind the baths 9 and 10 is mounted a pair of squeezing and advancing rollers 14. Between the rollers both materials, wetted in the respective baths, were pressed together.

After exposing, the negative material will be put in the apparatus according to arrow 16 and the receiving material 1 according to arrow 15, and both materials will bewetted and guided to the pair of squeezing and advancing rollers.

I claim:

1. In a silver salt diffusion transfer method, wherein an image is formed by exposure on the silver halide emulsion layer of a negative sheet and thus exposed negative sheet is developed by a developer liquid, whereupon the developed image is transferred by pressure contact to a receiving sheet, the improvement which comprises that the receiving sheet is uncoated sheet material which, prior to the pressure contact with the negative material, is moistened with a liquid compatible with said developer liquid, said liquid comprising an aqueous alkaline or acidic solution containing about I percent by weight of a tin (ll) salt or aluminum chloride, said liquid, per 1,000 ml. containing about I00 ml. of said solution.

2. The improvement as claimed in claim I, wherein said tin (ll) salt or aluminum chloride is added to the solution substantially immediately prior to said moistening.

3. The improvement as claimed in claim I, wherein said tin (ll) salt is formed in said solution by adding metallic tin thereto.

4. The improvement as claimed (ll) salt is tin (ll) chloride.

5. The improvement as claimed in claim I, wherein said liquid is an activator solution.

in claim 1, wherein said tin 

2. The improvement as claimed in claim 1, wherein said tin (II) salt or aluminum chloride is added to the solution substantially immediately prior to said moistening.
 3. The improvement as claimed in claim 1, wherein said tin (II) salt is formed in said solution by adding metallic tin thereto.
 4. The improvement as claimed in claim 1, wherein said tin (II) salt is tin (II) chloride.
 5. The improvement as claimed in claim 1, wherein said liquid is an activator solution. 